Storage stability problems are well known in enzyme containing liquids such as enzyme containing liquid detergents. This is especially true in protease containing liquid detergents.
The prior art has dealt extensively with improving the storage stability, for example by adding a protease inhibitor.
Boric acid and boronic acids are known to reversibly inhibit proteolytic enzymes. A discussion of the inhibition of one serine protease, subtilisin, by boronic acid is provided in Molecular & Cellular Biochemistry 51, 1983, pp. 5-32.
Boronic acids have very different capacities as subtilisin inhibitors. Boronic acids containing only alkyl groups such as methyl, butyl or 2-cyclohexylethyl are poor inhibitors with methylboronic acid as the poorest inhibitor, whereas boronic acids bearing aromatic groups such as phenyl, 4-methoxyphenyl or 3,5-dichlorophenyl are good inhibitors with 3,5-dichlorophenylboronic acid as a particularly effective one (see Keller et al, Biochem. Biophys. Res. Com. 176, 1991, pp. 401-405).
It is also known that aryl boronic acids which have a substitution at the 3-position relative to boron are reversible protease inhibitors. In WO 92/19707, acetamidophenyl boronic acid is described as an inhibitor of proteolytic enzymes.
Moreover EP 0 832 174 describes phenyl boronic acid derivatives substituted in the para-position with a >C═O adjacent to the phenyl boronic acid have good capacities as enzyme stabilizers in liquids.
There remains room for improvement in formulating, manufacturing and packaging liquid enzyme compositions that include sensitive enzymes to provide detergent compositions that do not loose enzyme activity during shipment and storage.